Bob wrote:
A three terminal regulator, properly chosen, will do a great job down at audio.
Depends on what you mean by "great job." All of the 3T regulators I'm familiar with have at least two orders of magnitude more noise than a well-designed LN analog regulator -- many have much more (especially LDO parts). At the low impedance levels involved, it's challenging to filter it out.
Finding inductors that will work from a few tens of KHz to a MHz while moving over an amp - much easier than at 30 Hz. * * * Next stop above that - something designed for RF. * * * The net result is a gizmo that's quiet, small, and low dropout.
In both of these ranges, the high current switching transients of the switcher tend to get into everything, including "grounds." There are resistive drops ("ground loops") plus inductive and capacitive coupling (every wire/trace is an antenna). It takes great care with layout and design to reduce these even to a dull roar, and extraordinary measures to clean up a switcher for precision analog work between DC and several MHz.
I'm not saying it can't be done, but it is a lot of work and you have to know exactly what you are doing in an environment where it is very hard to measure what you are trying to eliminate. It almost always involves shielding each module separately, using feedthrough capacitors from module to module, etc. Most of this can be avoided by using only analog regulators.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
